1. Field of the Invention
The invention relates to a method for closed loop control of the air system in an internal combustion engine, in particular a diesel internal combustion engine, with a first actuating element for recirculated exhaust gas in the exhaust gas recirculation tract and a second actuating element for air in the inlet tract, the two actuating elements being adjusted as a function of each other, and also to a device for carrying out the method. Furthermore, the invention relates to a method for controlling the characteristic values of combustion in an internal combustion engine with at least one control path.
2. The Prior Art
U.S. Pat. No. 6,105,559 B discloses an inlet and exhaust gas recirculation system for an internal combustion engine, the actuators, the exhaust gas recirculation valve and throttle flap being actuated as a function of each other by a single actuating element (actuator). The two actuators are joined together by a mechanical coupling. Only one actuating element and one controller are provided.
A diesel internal combustion engine with an inlet system and an exhaust gas recirculation system is known from U.S. Pat. No. 6,732,723 B1, an actuator being arranged in the inlet tract and an actuator in the exhaust gas recirculation tract. The two actuators are connected to the output of a single controller. A rigid logic divides the actuating signal at the controller output onto the two actuating elements.
The behaviour of the controller used in the prior art for both actuating elements represents a compromise, as a result of which the controller can be optimally configured for neither of the two controlled systems.
A further drawback is that the given structures impose marked restrictions in the selection of the actuating element boundaries. This gives rise to the problem that the controllery bandwidth is small and a different division of the actuators for other modes of operation is possible only to a limited extent.
It is known to control combustion in a stationary manner, i.e. at an operating point with a specific filling of the cylinders, via at least one injection parameter, in such a way that the characteristic values for the actual combustion and the desired combustion correspond. Deviations in the filling are compensated for by a controller in the air control path until the actual and the desired filling correspond. The target values for combustion in the stationary mode are datafied over the course of the calibration process. In this case, the target value for a reference variable is defined at an operating point. The target value is considered in conjunction with all other operating states at this operating point (in particular the filling). The stationary target value for the filling is stored in a memory at the same time as the target value for combustion. In this case, the actuators which determine the filling are set in such a way that the actual filling and the desired filling are equated. Based on the target value for the combustion position and the feedback about the actual combustion, the set parameters for combustion are changed in such a way that the actual combustion approximates the desired combustion. The adjustment variables are typically injection parameters, such as the moment of injection, injection pressure, quantity injected or the like. These can be adjusted (as a function of the injection system) at least within a combustion cycle. At the transition from one operating point to another, it is possible for the combustion control means to set the new value for the adjustment variables in a very short time. Nevertheless, the filling of the cylinders has based on the fuel control path a very different time constant, as a result of which the adjustment values for combustion in the fuel control path transiently do not match the current filling. This leads either to increased emissions with increased combustion noise or to low engine torque while at the same time consuming an increased quantity of fuel. In the past, these interactions could be reduced only at very great expense.